Caoimhín's Content

Welcome back to another Irish language video about astronomy, I endeavor to put out at least one Irish language video a month on this channel/website, and given the month that we are in, this one looks first at the longest night. In Irish, the month of December is “mí na Nollag” and Christmas is “Oíche Nollag”. Although “Nollag” looks very Irish, it is actually an old borrowing from Latin, coming from a word meaning birth, so it’s really birth-month and birth-night.

December is the month of the winter solstice, the shortest day of the year and the longest night. The longest night of the year is of course a fantastic time for astronomy, giving you more time than ever to observe the stars. This year however there is a problem, the Moon. The Moon is almost full on the night of the 22nd this year, so there will be a bit of extra light in the sky almost all night long. The light of the Moon can easily obscure fainter objects in the sky, so if you plan on looking at nebulae or galaxies, it might be worth waiting till the end of the year, when the Moon is closer to a New Moon and the sky will be nice and dark after sunset.

Of course, while the Moon is up we might as well take a look at it, and it is in an interesting phase. Just between a Half Moon and a Full Moon means that the Moon will be with us for most of the night, but we still get to see some of the texture. When part of the Moon is in shadow, we can see the peaks of mountains and hills catching the light, and craters casting shadows. This makes the line between night and day a little wobbly, and shows the locations of craters very clearly. When the Moon is full, large portions of the Moon can look very flat, almost smooth, but the right phase will show the real texture of the surface, covered in cracks and craters. The Moon might get in the way of other objects, but luckily it’s a nice object to observe all on its own.

To make things a little easier to see, I push ahead a few days bringing the Moon out of the sky and giving us a chance to see Vesta, which you may remember from the last video. The previous video here was all about asteroids and Vesta is one of the biggest. However, looking at Vesta last time, Stellarium informed me that its orbital data might be out of date! This can lead to errors in its position in the sky, so of course I updated the software immediately afterwards. The new update thankfully confirmed that Vesta was basically in the exact same place, so no retractions or corrections needed.

The newer version of Stellarium, 0.23 other than the 0.21 I’ve been using till now, has a couple of differences. Firstly, a lot of the text and interface panels are larger, probably useful on larger screens, but also hopefully easier for you to see in these videos as well. The new Stellarium software update came with some updated names and labels on certain objects, and that leads me to the next topic, exoplanets.

Exoplanets are simply planets around other stars. We’ve known that they exist for almost two decades now, and Stellarium has provided a feature to highlight them for a few years at least. By dropping down the light pollution levels, it becomes clear that there are thousands and thousands of them, with a particularly dense grouping up at the top of the Summer Triangle, between Deneb and Vega. This is the field of view of the Kepler Space Telescope, a telescope made especially for hunting planets. Kepler observed this part of the sky and only this part of the sky for years, and discovered thousands of telescopes all on its own.

It’s though that around 400 Kepler’s would be needed to cover the whole sky, and if we did have them they’d all probably discover a similar number, which would lead millions of known exoplanets. Unfortunately, there aren’t plans for that kind of massive observational effort any time soon. Although, it could be a good thing, as astronomers already had a tough time keeping up with all the discoveries made by just one Kepler. For example, there wasn’t really time to name all of these new discoveries in an interesting way, they all got named after Kepler, Kepller-1, Kepler-2, Kepler-3 . . . Kepler-1300, Kepler-1301, up to almost 2000 so far. For each of these, the planets were assigned letters, “a” for the first, “b” for the second, and so forth through the alphabet for systems with many planets.

This method was used for other surveys as well, leading to hundreds and hundreds of planetary systems with very similar, and slightly boring names. this situation didn’t just occur because astronomers are bad at naming things, there is some planning necessary to name stars. In ancient times, people named what they could see in their own languages, and the astronomical records from ancient times give us loads of Greek, Latin and Arabic names. With the prestigious nature of Latin, it kept being used to name things into modern times. However, there are a lot of languages on Earth, and it doesn’t seem very fair for just a few to have all the glory.

Luckily, there is a group in charge of names, for planets, stars and astronomy in general, the IAU, the International Astronomical Union. This is the group that voted for Pluto to be reclassified as a dwarf planet. It is truly international, with over 100 member nations. To ensure that the new planetary systems were named in a fair and representative way, 100 were selected, one for every member state. Of course, Ireland is among those members, and we were given HAT-P-36.

The High Altitude Telescopes 36th planetary system, the star HAT-P-36 and its planet HAT-P-36b, were the ones given to Ireland to name. This system happens to be visible from Ireland all year long, circling the Pole Star as the Earth rotates, at least until the Earth starts pointing in a different direction, you can check out my past video on longer timescales to learn more about that. It rests in the constellation of Canes Venatici, the Hunting Dogs, just under the handle of the Plough or Big Dipper. The Irish public were given a chance to submit names for this star and planet, which were then narrowed down by a team in Blackrock Castle Observatory in Cork City.

Tuiren and Bran are the new, more human, names for this star and planet. According to mythology, Tuiren was once a young woman who was turned into a dog, and while in canine form gave birth to two pups, Bran and Sceolán. Because they were born as dogs, that was their true form, where as Tuiren was able to regain a human form, the dogs were stuck that way. They went on to become legends in their own right, and I will talk about them more in the next video, giving an English language explanation of these distant planets. For now, what matters is that we have a star and planet named in Irish, and many more countries can now say the same about their own native languages.

To finish up we return to the morning of the shortest day, to watch the sunrise. Rather than rising in the East, it comes up in the South-East! This may seem strange, but the exact point where the Sun rises changes over the course of the year, reaching its most southerly for us in the Northern Hemisphere on the Winter Solstice. This is the principle upon which Newgrange in Ireland functions. Only on the morning of the Winter Solstice will the Sun shine down the passage tomb, illuminating it briefly, and only on one day of the year. The day after the solstice, the Sun rises a little more to the East, and it doesn’t come back until a year has past. Even ancient Irish people knew this phenomenon, even if they didn’t know that it was due to the Earths tilt, they new it well enough to build the massive earthwork that is Newgrange around it.

Now of course you know it as well! I’ll be posting a video all about exoplanets and reviewing Tuiren and Bran in English soon, if you’d rather not read the subtitles, so I hope you’ll join me back here then.